Electrons doped in cubic perovskite SrMnO3: isotropic metal versus chainlike ordering of Jahn-Teller polarons

TL;DR

This study investigates how electron doping in cubic SrMnO3 influences its magnetic and electronic phases, revealing a transition from an isotropic metal with Jahn-Teller polarons to a chainlike orbital-ordered insulator.

Contribution

It provides a systematic experimental analysis of doping-induced phase transitions in SrMnO3, clarifying the role of Jahn-Teller polarons and orbital ordering in this canonical system.

Findings

Low doping (1-2%) results in a G-type antiferromagnetic metal with Jahn-Teller polarons.

Higher doping (>4%) leads to an insulating phase with tetragonal distortion and orbital ordering.

The results highlight the importance of cooperative Jahn-Teller effects in phase evolution.

Abstract

Single crystals of electron-doped SrMnO3 with a cubic perovskite structure have been systematically investigated as the most canonical (orbital-degenerate) double-exchange system, whose ground states have been still theoretically controversial. With only 1-2% electron doping by Ce substitution for Sr, a G-type antiferromagnetic metal with a tiny spin canting in a cubic lattice shows up as the ground state, where the Jahn-Teller polarons with heavy mass are likely to form. Further electron doping above 4%, however, replaces this isotropic metal with an insulator with tetragonal lattice distortion, accompanied by a quasi-one-dimensional 3z^2-r^2 orbital ordering with the C-type antiferromagnetism. The self-organization of such dilute polarons may reflect the critical role of the cooperative Jahn-Teller effect that is most effective in the originally cubic system.